The invention relates to the field of converters, such as boost converters and buck converters for example, as well as rectifiers and inverters, for example those used in uninterruptible power supplies, in particular in high-power uninterruptible power supplies, i.e. with a power generally comprised between about 100 and 500 kVA.
The invention relates more particularly to a converter device enabling first electric voltages available on a first, second and third voltage line of a first type to be transformed into a voltage on a voltage line of a second type, in either direction, said device comprising:                a first main switching unit connected to said first voltage line of the first type and equipped with a first main switch,        a second main switching unit connected to said second voltage line of the first type and equipped with a second main switch,        a main switching point connected to said voltage line of the second type and connected to said first and said second main switching unit, and        a third main switch common to said first and to said second main switching unit, said third main switch being connected between said main switching point and the third voltage line of the first type.        
The invention also relates to an uninterruptible power supply comprising a power supply input on which an AC input voltage is applied, a rectifier connected to said input, two substantially DC voltage lines of opposite signs connected on output of said rectifier, and an inverter connected to said substantially DC voltage lines and comprising an output designed to supply a secured voltage.